Object Inheritance Without Classes

Abstract

Which comes first: the object or the class? Language designers enjoy
the conceptual simplicity of object-based languages (such as Emerald
or Self) while many programmers prefer the pragmatic utility of
classical inheritance (as in Simula and Java). Programmers in
object-based languages have a tendency to build libraries to support
traditional inheritance, and language implementations are often
contorted to the same end. In this paper, we revisit the relationship
between classes and objects. We model various kinds of inheritance in
the context of an object-oriented language whose objects are not
defined by classes, and explain why class inheritance and
initialisation cannot be easily modelled purely by delegation.